Process for preparing diolefins from ethylene, steam, and calcium carbide



Nov. 13, 1945. c. H. HOLDER PROCESS FOR PREPARING DIOLEFINS FROM ETHYLENE,

STEAM AND CALCIUM CARBIDE Filed June 18, 1943 Patented Nov. 13, 1945 ample PROCESS FOR PREPARING DIOLIIFINS FROM gllfilnYLENl, STEAM, AND CALCIUM OAR- Clinton 1!. Holder, Cranial-d, N. 1., asslgnor to Standard ration of Delaware Oil Development Company, a corpo- Application June is, 1943; Serial No. 491,313

it Claims. (on. eta-cs) The present invention relates to improvements in the synthesis of butadiene, and in particular it relates to an improved process for synthesizin butadiene from acetylene and ethylene.

The production of synthetic rubber and rubber substitutes has become 'an important problem. Numerous proposals have been made for preparing rubber substitutes and rubber-like materials. Several of these processes involve the use of a diolefin known as butadiene. For example, a rubber substitute suitable for manufacturing a rubber-like material suitable for making automobile tires may be prepared by condensing together or copolymerizing, butadiene and styrene.

There are a number of methods for making butadiene, which involve a variety of starting materials. One of the most practical general sources of butadiene is the petroleum, field, even though butadiene is not produced in substantial quantities in any common or conventional petroleum refining operation. However, relatively large quantities of ethylene are produced in cracking, reforming, dehydrogenation and other commonly used processes in modern petroleum oil refinery practice.

My present invention takes advantage of the fact that reasonably large quantities of ethylene are available in the ordinar refinery as a result of normal operations, and at the same time, further quantities of ethylene could be specially produced. As to the acetylene which I condense with the ethylene to form butadiene, I propose to form that material by treating powdered calcium carbide in the form of a "fluidized" mass, with steam and to react the nascent acetylene thereby released with the ethylene in situ and in the presence of a catalyst, calcium oxide, to form substantial quantities of butadiene, all of which will more fully and at large appear, hereinaiter. i

In order to facilitate understanding of my inventi'on, I have shown in the accompanying drawing, diagrammatically, a flow plan indicating the important steps of my process.

Referring in, detail to the drawing, I provide a source of calcium carbide ground to a particle size of from 200-400 mesh, with a size of around 300 mesh predominating in the mixture, in an elevated closed hopp r I. However, in order to conserve grinding costs much coarser particles may be used for instance up to /2 inch diameter, although to 1 inch is a preferred particle size range. The closed hopper I is in communication with an elongated standplpe 3 through a star feeder 2 and terminates in a bend I 0 projecting is injected into the lower bend in of the stand-' pipe 3 where it mixes with the calcium carbide which descends from the hopper i through standpipe 3 and forms a suspension ormixture which is swept into the reactor 20 through the ioraminous member 22, previously mentioned. Meanwhile steam from some source is also discharged into the reactor through a pipe 8.

Referring again to the standpipe 3, in order to facilitate the fiowability'or to fluidize, the calcium carbide therein, it is found desirable to inject into the standpipe through taps 5, small quantities of a gasiform material, which in this case may be ethylene or an inert gas such as flue gas. The ascending steam, ethylene-and other gas or vapors in reactor 20 is controlled as to superficial linear velocity, within the limits of l-Bft. per second, preferably 1 /2 to 3 ft. per sec ond so as to form with the calcium carbide the fluidized mass of solids previously referred to, which mass will have an upper dense phase level at L. This fiuidized" mass is in the form of a turbulent, ebullient mixture of vapors and solids and is referred to as "fluidized because of its particle mobility and its resemblance to a boiling liquid. The vapors after passing through reactor 20, thence fiow into an expanded disengaging chamber 25 where the linear velocity ofthe gases is reduced to say ft./second, due to the greater diameter of the chamber 25, at which velocity the gases and/or vapors will not support fully the solids and the latter gravitate into the main body of reactor 20 so that the gas is eventually substantially freed of entrained solids. Thus, where the density of the material in the reactor 20 is from 15-25 lbs/cu. ft., the density of the gasiform material in line 30 may be of the order of 0.025 to 0.050 lb./cu. ft.v I provide a bottom drawofi pipe 26 projecting, as shown, into the reactor 20. In order to facilitate withdrawal of this product which will be, largely, calcium oxide or calcium hydroxide, I bleed into the draw-oil pipe 26 through a plurality of taps 2'! a gasiiorm material which may be steam, flue gas, CO2,

ethylene, and the like; The draw-oil pipe 26 has a flow control valve 29, and also the standtherein suflicient solids to provide the fluidized mass with the density indicated and continuously draw-enpirerl.

withdrawlimeor Y gues s Theproductis-withdrawn line a,

in addition to lmtadiene,rsteam,-un-' reacted acetylene, ethylene, and as benzene-and various other order to recover the butadiene, I propose to cool the materials suiliciently to condense 1 Itis out that or emp oying a standpipc tofeed the calcium carbide into the roactoryl-l mayiemploy other feeding means such and thereafter to fractionatethe remaining hydrocarbons' to recover the butadiene. course,

acetylene. r i larl wh nrams ma is a. material somewhat dangerous to handle since it- .;isliablge toexplode, but when diluted orque'nched wi h hy r a n the s nsiti lw in this ret r is reduced. Another good wayof decreasing the sensitivity of acetylene to explosion would be to iniect. a small quantity of ethylene through 28 into chamber ll. sinceethylene is especially eirective mthis regard. The products in line II. 'are then through awaste heat boiler 3| to cool thejsame and thence passed through a second cooler it where they-are cooled below the condensation point of steam and thence'discharged into a water separator is from which water may be withdrawn through line It, while the gaseous hydrocarbonsaref'taken of! overhead through line "and thence passed into a frac- .tionator It. The benzene and other normally liquid hydrocarbons may be withdrawn from the iractionator through line ll, while the Csand lighter hydrocarbons may be withdrawn overhead as a screwconveyor. Thus, I may discharge say powdered calcium carbide into feed hopper .32 andcause thepowdered to be fed to the reactor by theoperatiod or screw feeder It shown) operating on pulley. 35 or-other driver means or the said conveyor. The steam and 'ethylene'wol'lid'be. iedinto the bottom otthe reactor as'sbove,-in.tllis-modiflcation.

AsQangillustration of the operation of the above motivated by afsuitable driving means (not described process-under a preferred set oi conditions, and using tbe-appar'atus illustrated in the drawing, a mixture of steam fand ethylene is passed throuah the reaction zone with an amount or 200 mesh calcium carbide such that the weight r ratio or the ethylene-steam mixture to the calcium carb ide isabout 0.8; the linear gas velocity in ther'eactor is aboutl-fi ieet per second; the

. in the reactor is about lbs/sq. in;

through line it. The Ct fraction containing the butadiene may be withdrawn as aside stream through'line as and subiectedto redistillation and/or solvent treating. it necessary, to recover commercially pure 'butadiene. separation ofbutadiene iromYother C4 hydrocarbons, such asisobutane, butane; normal butene, and isobutyl enes is well known to familiar with fill-I artand need not be described'in detail. Bumce it tour that someoi these hydrocarbons'maybe.

separated by close fractional distillation, while others such as butane-1 may not be so separated, and one good'practice is to subject them to a vapor-liquid solvent treatment wherein the butadiene passes into the extract phase while thebutene-i or butene-2 is'undissolved-by the sollbs./sq.- in. As to the proportion of reactants the; steam should be somewhat in molal excess (5 in the reactor) to 5 minutes.

vent. A satisfactory selective solvent for separating butadiene from butene-l and butene-ii is copperacetate in ammonia.

Having generally described a preferred method higher pressure, .also

products.

gauge,-and the temperature-about 850? E: and

the foregoing briefly, my invention relatesto a method of producing butadiene by copolymerizing and/orccndensing together acetattemperatures of from about 700 to 1100' F.

which-fare most favorable for the reaction be- .tweenethylene and acetylene to form butadiene. The ethylene isprepared in known manner, for example, by steam cracking at high tempera-- tures, or from any 'oi the normal petroleum reflnery operations It is pointed outthatinad dition to obtaining butadiene, my process also results in the production of other dioleflns such as pentadiene or isoprene- Also, side reactions.

of operating my process, I now disclose the preferred operating conditions in reactor 20. Ithas been found that acetylene reacts with ethyleone at about 850 F. to give 3il% yields-and this may be increased to ongi'eediby recycling oithe unconverted productsi-As regards the pressure prevailing in reactor 2|, the same should be of'the order of atmospheric, pressure to .100

to 10%) oithe stoichiometric proportion tor the carbide-steam reaction." Ethyleneshouldbe in molal slight excess (say 10% of the, theoretical) oi' the available acetylene, that is to say there should be about 1.1 mols of ethylene ioreachmol 1.0 weight of iced gases. per'we sht or carbide per hour have been found satisfactory the range 0.1-to 5.0 weights of feed gas per weight of calcium carbide per hour be used. Steam may-be employed to vary the feed rate.

Contacttime's (i. e. residencetime of reactants should be oftheorder oft '75 as aromatics and alkylated derivatives thereof, areiormed. Of course,inmyprocess0a0orthe equivalent or burnt lime will alsobe produced at the high temperatures involved. V

, My process aiiords several very desirable teatures. -By generating-acetylene in the hot'aone nascent acetylene which appears to be more reactive than ordinary acetylene is produced in contact with the desired reactant. ethylene.

. I'hus,'the necessity of heating the acetylenesepaoi acetylene in reactor". Feed rates of about obtained by virtue of the fact that the continuously iormed fresh supply or calcium oxide is a catalyst for the cop lymerization-oi acetylene and ethylene to i'orm. butadiene. The fluid" technique permits flexibility of operation so that the .exothermic heat of the carbideesteam reaction may be utilised-to advantage. Also,..be-

"cause of. the exothermic nature of the reaction i between steam and calcium carbide it is possible to utilise the heat of reaction to bring the rea'ctants to the desired temperature and thereby I cabfl-moceo- -cim AH=+i43e6 calsJmoLoiCaC: I

, the dimensions or the reactorare chosen so that I 'yiene and v ethylene, The. acetylene is produced I by treating powdered calcium carbide with steam rately with the attendant possibility of causing polymerization is avoided. Further advantage is achieve heat The reaction involved together ,with the heat releasedis set forth-below:

aesaare The fluidized condition of the calcium carbide affords a convenient means of uniformly distributing the heat of reaction. Further control on the temperatures inside reactor 20 is possible by preheating the steam and/or the ethylene to reach higher temperatures or to achieve the opposite purpose, an excess of steam may be used in the capacity of a cooling gas in order to lower the operating temperature. The introduction of the reactants in the manner specified above permits the formation of nascent acetylene at reaction temperature and in the presence of the second reactant, ethylene. In addition the calcium oxide resulting from the steam-calcium carbide reaction is a catalyst for the copolymerization of acetylene and ethylene which it is desired to promote.

Numerous modifications of my invention falling within the scope thereof may be made by those familiar with this art without departing from the spirit of my invention.

What I claim is:

1. A continuous method of forming butadiene which comprises feeding subdivided calcium. carbide into a reaction zone, simultaneously feeding ethylene and steam to said reaction zone, causing the calcium carbide-to form a fluidized mass in the reaction zone by controlling the linear velocity of gasiform material within the reaction zone within the limits of /2 to 6 feet per second, permitting the reactants to remain in contact with each other at elevated temperatures for a sufllcient period of time to effect the desired reaction and recovering from the reaction zone, vapors containing butadiene.

2. The method specified in claim 1 in which the temperature within the reaction zone is from 700 to 1100" F.

3. The method of continuously synthesizing butadiene in a reaction zone which comprises continuously forming acetylene in said zone by reacting calcium carbide with steam at temperatures of from 700 to 1000 F. and continuously feeding ethylene into said zone where it contacts nascent acetylene.

4. The method of claim 3 in which the calcium carbide is maintained in a fluidized mass by controlling the linear velocity of gasiform material in the reaction zone between /2 to 6 feet per second.

5. The method of claim 3 in which the term perature in the reaction zone is about 850 F.

6. The method of claim 3 in which molai concentration of ethylene exceeds that of the acetylene in the reaction zone.

"I. The method of claim 3 in which direct steam is employed to temper the exothermic reaction taking place between acetylene and ethylene.

8. The method of claim 3 in which crude butadiene vapors containing unreacted acetylene are withdrawn from the reaction zone and immediately quenched.

9. A continuous process of synthesizing butadiene which comprises continuously feeding powdered calcium carbide to an elongated vertical confined reaction zone. simultaneously feeding steam and ethylene to the reaction zone to inlets at near the bottom thereof, permitting the ethylene and steam to flow upwardly within said reaction zone at linear velocities of from about V2 to 6 feet per second whereby the powdered calcium carbide is maintained in a fluidized state, maintaining the temperature within the reaction zone between 700 and 1100 F. by control of the entering steam temperature and the amount thereof, permitting the steam and calcium carbide to contact each other for a sufllcient period of time to form acetylene, which acetylene in .nascent state reacts with the ethylene to form butadiene under the temperature conditions specified and withdrawing vapors containing butadiene from the reaction zone.

10. The method of claim 9 in which the temperature within the reaction zone is maintained at about 850 F.

CLINTON H. HOLDER. 

